Dosage-dispensing devices for free-flowing substances, for example powders, pastes or liquids, are used in many areas of industry. These dosage-dispensing devices are preferably equipped with a drive mechanism, a controller, and a measuring device to measure the amount of material dispensed. The free-flowing substance, i.e. the material to be dispensed, can be supplied to the dosage-dispensing device either through a feeder conduit or by means of an exchangeable dosage-dispensing unit. To allow the dosage-dispensing unit to be set into the dosage-dispensing device, the latter needs to be equipped with a holder device.
A dosage-dispensing unit is essentially composed of a source container which holds the dosage material and a dispensing head which closes off the container. The dispensing head has an outlet orifice and a shutter element, by means of which the outlet orifice can be closed to a variable degree. In place of the source container, the dispensing head can also be supplied with dosage material by a conveyor device, for example a feeder hose.
A dosage-dispensing device with a holder device for a dosage-dispensing unit of the aforementioned kind is disclosed in commonly-owned and co-pending US published application 2008/0190513. The holder device of this dosage-dispensing device is pivotally supported on a horizontal axis. Oscillatory pivoting movements of the holder device can be generated by means of an impact mechanism, whereby dosage material in powder form inside the dosage-dispensing unit is loosened up. The pivoting movements further have the effect of breaking up material bridges in the powder material, which impede the free flow of dosage material to the outlet orifice. Material bridges are formed when individual powder particles become mutually locked into an arc-shaped barrier and thus stop the continuous stream of dosage material to the outlet orifice.
Oscillatory pivoting movements produced excellent results in dosage materials in power form with granules of any shape and with low moisture content. The dosage material contained in the dosage-dispensing unit, which has been solidified due to long-time storage, transport vibrations or moisture absorption, can be brought back into a significantly more free-flowing condition by the pivoting movements. This is due to the fact that the dosage material is tossed up inside the source container, whereby the dosage material is turned into a loose aggregate.
However, experiments have shown that in spite of the loosening-up, the dosage material clings to the interior wall of the dispensing head, particularly in the area of the outlet orifice. This can become an obstacle to the dosage-dispensing process.
There is, therefore, an objective to create a dosage-dispensing unit in which as little as possible of the dosage material remains stuck to the inside wall of the dispensing head.